Z.B.
Everything you mentioned is normal for a 2 month old.
Spitting up a lot - Some babies spit up. What seems like a lot to us might not be very much.
sleeping less - Lots of babies do not sleep consistently for a few months. Mine didn't sleep well until they were about 4 months.
fussy - Babies get fussy. It's hard to know what they want. Are they hungry, wet, poopy, tired, need to snuggle, need to move, swing or rock.
poops about once a day - very normal. They poop so much and so often as newborns that it can seem alarming when they don't poop as often. But once a day or every couple of days is normal.
loose and green - Well, yes, it's loose. He's on a liquid diet, so it won't be firm. Isn't green normal for formula? Sorry, it's been awhile.
Honestly, you have to trust the doctors and follow their instructions. I would only make a formula change if a doctor recommended it. Changing formulas too often and/or two quickly can be very hard on their little tummies.
Trust the doctor!